Consider the following conversation:
— Мђша, гдљ вІ бІли вчерђ? На футбћле? "Masha, where were you yesterday? At the soccer game?"
— Дђ, ї вчерђ ходќла на футбћл. "Yes, I went to the soccer game yesterday."
— ВІ вќдели Сђшу? "Did you see Sasha?"
— Дђ, ї егћ вќдела, когдђ ї шлђ на мђтч. "Yes, I saw him as I was going to the game."
The Non-One-way verb ходќть is used in expressing 'I went to the football game,' above, because the motion is not in one direction — it is a round trip. But the One-way verb идтќ must be used in expressing 'as I was going (as I was on my way) to the game' because the motion is in one direction.
The English expression 'on my way', though sometimes a clumsy translation, expresses the idea 'One-way' quite well, and may be useful for you to bear in mind. English and Russian can both express the idea 'One-way', but the two languages do it differently, and Russian forces you to express it, while in English it is optional.